The present invention relates to improved apparatus for thermal treatment of semiconductors in a treating gas.
In conventional apparatus for thermal treatment of semiconductors, a treating tube has a sealing cap mounted on one end of the treating tube, near an outlet of the treating tube for discharge of a treating gas. A substantial portion of the treating tube is heated so as to form a region of uniform heating temperature extending longitudinally within the treating tube.
Since the treating gas at high temperature contacts the inner surface of the sealing cap, heat energy is released from the outer surface of the sealing cap, whereupon energy losses are great. Also, convection currents are formed in the treating gas, because of the temperature difference between the sealing cap and the high-temperature zone within the treating tube. Hence, convection currents are formed between the treating gas cooled within the sealing cap and the treating gas present in the high-temperature zone, in a neck of the treating tube, so as to form a local low-temperature region within the treating tube. As a result, the region of uniform heating temperature extending longitudinally within the treating tube is shortened.
In a copending U.S. patent application filed simultaneously herewith and assigned commonly herewith, it is disclosed that convection-preventing plates may be disposed within a treating tube so as to interrupt currents of the treating gas, whereby the region of uniform heating temperature extending longitudinally within the treating tube is shortened.